My DIY subwoofer project

[CECAA850]

If and when I try the corners, it will not be an easy proposition for me. I will have to remove the large 8' corner bass traps in order to place the subs in the very corner of the room. So, it will be a project for one of those rainy days.

You might try some of those furniture "slider" discs. It may make the move a little more tolerable.

[Rudy81]

Oh yes. I have used those furniture sliders when zeroing in on where to place my RSW-15s. Made it much easier to move them around until I found the sweet spot for those monsters.

[Pete H]

You might try some of those furniture "slider" discs. It may make the move a little more tolerable.

If they could just make a set that would slide up and down steps! Carried one of the RSW 15's up the steps last night to play and that sucked, but I would rather carry that than the RF 7's or the Cornscala's.

[Rudy81]

I feel your pain all too well. One of the things that suck about having the media room upstairs is that it is, well, upstairs. I have lugged Khorns, RSW-15s, DBBs, amps, and DIY subs up there. What a hassle.

[mikebse2a3]

If and when I try the corners, it will not be an easy proposition for me. I will have to remove the large 8' corner bass traps in order to place the subs in the very corner of the room. So, it will be a project for one of those rainy days.

Rudy I don't know what frequency you are crossing at but if you keep it below 40Hz(ie: a 28' wavelength) and especially if you use a fairy sharp crossover then experimenting locating the sub close to the corner but not necessarly snug in the corner could be a very good option and you might still benefit from the corner traps still being in these corners.

mike tn

[dtel]

How much difference is there with the second sub ? I was planning on a L & R corner placement, stereo kind of. Have you tried with just one sub running ?

[Rudy81]

How much difference is there with the second sub ? I was planning on a L & R corner placement, stereo kind of. Have you tried with just one sub running ?

No, I have not tried it with just one sub. I can certainly do that. I suppose I will just lose 3dB or so. I can measure the change when I do it by just muting one channel and seeing what kind of change I get.

I will have to check with Mr. Hurd again on the L/R corner placement vs. putting them close to each other to act as one. I know there are other issues to consider when splitting the subs up like that.

[Rudy81]

Mike: I am not specifically crossing the subs at any frequency. Let me explain. The DIY subs are hooked up to the LFE or .1 output of my pre/pro. It has the capability to send anything below 125Hz to that channel which is encoded in the movie soundtrack. So, if it is in the soundtrack and is below 125Hz, it is sent to the DIY subs.

I am certainly aware of the potential benefits of placing a sub in the corner of a room. Having 2 subs, I have quite a bit of flexibility. I can keep them together in one corner, or split them up and place each one in a corner. Lot's of options. I will have to play around with the options.

[mikebse2a3]

I will have to check with Mr. Hurd again on the L/R corner placement vs. putting them close to each other to act as one. I know there are other issues to consider when splitting the subs up like that.

Rudy placing subs together has the effect of basically creating one larger sub but doesn't give you many options/benefits when it comes to coupling those subs to the room.

As Toole's experiments proved if you can locate multiple subs at multiple points in the room(with some EQing for each sub also giving some improvement) a listener can acheive some real world benefits.

mike tn

edit: Rudy I just read were you are using it up to 125Hz so yea lots of variables integrating it with the room and the mains.

[Rudy81]

I will work on various locations when time permits. It would be very interesting to see what Audyssey Pro does with two subs in two different corners.

[Pete H]

I feel your pain all too well. One of the things that suck about having the media room upstairs is that it is, well, upstairs. I have lugged Khorns, RSW-15s, DBBs, amps, and DIY subs up there. What a hassle.

I'm not sure how old you are, but I'm guessing that your are at least 10 years younger than me (45) and if I'm right and your whining now[:'(] sorry couldn't help it[], I had to walk away from the keyboard for just a minute to compose myself, and no, I didn't need to change my depends, I'm only 45............ but let me tell you there's a time in your 40's where you go darn, I could have carried 3 of those while drinking a beer a couple of years ago. Until a year ago I could see everything and it was like all of a sudden there was a distance that was all fuzzy (not warm and fuzzy, just fuzzy) it sucks!

Oh, my gosh, I just realized that I'm Jacksonbart with a brain (I'm sure he's not going to read this thread, it's too long and informative). Actually, Jackson has provided me with quite a few laughs and I'm glad he's on this forum...........................most of the time.

On a totally serious [8], There are a few people on this forum that are in the same space that I am and I know that when the opportunity comes to hang out and socialize, we'll probably get arrested " Watch the movie Very Bad Things", but it will be something to tell the grandkids about! Love you guys and really wished you were closer since all of my friends where I'm at think I'm way over the top with the audio quest, but I'm O.K. with that, because I can come to Audioholics Anonymous and feel O.K.

On a last note, for all of you Homo-phobics out there, you can tell other men "Love you man" and not want to go all Girble on their as&,( I should really write this stuff down and do a little stand up"

I hope you all have a wonderful evening...........................crap, I'm out of Jamison.[]

[Rudy81]

Pete, as I sit here enjoying a glass of Glenfiddich, I realize your power of deduction sucks! []

I'm 52, so a little respect for your elders please!

Now, its not just lugging the beasts upstairs. The trick is that you are not allowed to damage, hit, rub on, puncture, or in any way fold, spindle or mutilate any of the doors, walls, stair steps, hand rails, or other house decoration! Lest you wish to test the ire of the Lady of the house. Being a single man, you may not understand that yet, but you likely will.

Having said that, I think you've had enough Jamison for the evening.

Good night.

[dtel]

Nothing wrong with 52 I spent the last year or so there.

The last two post on this thread are some of the funnest I have seen in a while. [Y]

[psg]

Pete is hilarious!

[michael hurd]

As Toole's experiments proved if you can locate multiple subs at multiple points in the room(with some EQing for each sub also giving some improvement) a listener can acheive some real world benefits.

mike tn

Read Welti's paper on multi subs. First, it's based upon Toole's work, and second it's a simulation based on a rectangular room with no door openings, no windows, 24 feet x 20 feet and 9 feet tall.

The simulation also is assuming even response over 16 seats, fitting into an fictional area of 6 feet x 6 feet.... 36 Sq ft.

Not possible. You could probably cram 2 theater seats into that area, for two people.

Also not possible: locating 50 subs randomly in the room or 5,000 subs.

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White%20Papers/multsubs.pdf

In short, it's an math exercise.

Cue Earl Geddes:

Advocates multiple high bandwidth subs located around the room, and only one ULF subwoofer. Unfortunately, unless you desire radiation from 80-120hz from multiple sources around the room, and limited ULF capability, then this is not what I would investigate.

I have spent some time helping out with measurement and optimization in a huge room for a friend in Wisconsin, located on a main floor open to all areas of the house. The room is somewhere in the neighborhood of 8200-10,000 ft^3 when you count in the 2nd floor hallway.

What I have found: random placement of wide bandwidth subs, reproducing the same LFE signal will give you good LF capability, but un-even mid and upper bass. What we tried, and eventually settled on: different bandwidths for each of the 4 subwoofers, and rotating the phase each output independantly with a Behringer DCX 2496.

The result was a much flatter FR over the main seating area. There is only one subwoofer that has a 125hz and down range, two that have a bandwidth of 80 hz and down, and the fourth subwoofer that is located behind the seating area ( nearfield ) has delay as well as a bandwidth of only 60hz and down.

Each subwoofer has minimal eq applied to it, once the phase was rotated to align it with the others. After all of the subwoofers were added, then the group was eq'd as a whole.

As you go lower in frequency, you effectively have more displacement. WIth the Geddes approach, you have the most displacement for upper bass frequencies, and limited displacement where it's needed, down low.

[michael hurd]

The three main subwoofers have dual opposed 18" TC Sounds LMS5400's, each box has ( 2 ) Crest 8002 amplifiers. Each amplifier is bridged and capable of 4KW into the 4 ohm load of each driver.

6 4kw amps = 24kw for the main subs, the nearfield sub was a TC 3000 on a Behringer EP2500, soon to be replaced by another 18" LMS 5400 on another Crest 8002.

Let's just say that headroom is 'adequate' and that output is not a problem.

[Rudy81]

Mike, thanks for chiming in. If I understand your explanation correctly, in my case, going from 120Hz down, I need to keep both subs together....correct? Also, do you think there would be any benefit to move the subs to either front corner, or leave them as they are mid room on the floor?

Thanks again for all your help.

[michael hurd]

If you move the subs to the side walls then you will lose some on the upper end of their response, and gain some on the low end in my opinion, however it would be an interesting experiment.

"Real" rooms never ever work like simple a simple model. Even as stated in the paper, the nodes and antinodes are skewed in the 'real' room to one side due to the door.

[Rudy81]

Mike, very good. I'm sure at some point I will run an experiment to see how things change by moving the subs around. For the time being, they are performing very well where they are.

[mikebse2a3]

Read Welti's paper on multi subs. First, it's based upon Toole's work, and second it's a simulation based on a rectangular room with no door openings, no windows, 24 feet x 20 feet and 9 feet tall.

The simulation also is assuming even response over 16 seats, fitting into an fictional area of 6 feet x 6 feet.... 36 Sq ft.

Not possible. You could probably cram 2 theater seats into that area, for two people.

Also not possible: locating 50 subs randomly in the room or 5,000 subs.

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White%20Papers/multsubs.pdf

In short, it's an math exercise.

Thanks Michael

I can't say it was just a math exercise at all IMHO.

The paper was both a simulation of a room (Note: the simulation was based on the actual real room used also) and an actual real room and yes the listening area was for the test purposes was 6' x 6' using 16 measurement points for valid data gathering and not in any reality that 16 actual listeners would fit in that space. It is often usefull to explore the extremes sometimes when investigating how something behaves and thats why in the simulation even 50 to 5000 subs were simulated and the results was a pratical limit of 4 subs with even 2 subs being reasonably close to acheive the goals of smooth frequency over multiple listener locations.

Cue Earl Geddes:

Advocates multiple high bandwidth subs located around the room, and only one ULF subwoofer. Unfortunately, unless you desire radiation from 80-120hz from multiple sources around the room, and limited ULF capability, then this is not what I would investigate.

I totally agree that this isn't a logical approach IMHO.

IMHO I wouldn't really want to run subs any higher than necessary and 80Hz (with a very sharp cutoff point) would be my upper limit especially if the main speakers are running full range and capable of good LF output themselves.

I have spent some time helping out with measurement and optimization in a huge room for a friend in Wisconsin, located on a main floor open to all areas of the house. The room is somewhere in the neighborhood of 8200-10,000 ft^3 when you count in the 2nd floor hallway.

What I have found: random placement of wide bandwidth subs, reproducing the same LFE signal will give you good LF capability, but un-even mid and upper bass. What we tried, and eventually settled on: different bandwidths for each of the 4 subwoofers, and rotating the phase each output independantly with a Behringer DCX 2496.

The result was a much flatter FR over the main seating area. There is only one subwoofer that has a 125hz and down range, two that have a bandwidth of 80 hz and down, and the fourth subwoofer that is located behind the seating area ( nearfield ) has delay as well as a bandwidth of only 60hz and down.

Each subwoofer has minimal eq applied to it, once the phase was rotated to align it with the others. After all of the subwoofers were added, then the group was eq'd as a whole.

As you go lower in frequency, you effectively have more displacement. WIth the Geddes approach, you have the most displacement for upper bass frequencies, and limited displacement where it's needed, down low.

I totally agree with this approach this is also what I was suggesting to Rudy in my post.

What you have just described is also written about in Toole's book (Floyd E. Toole, Sound Reproduction Loudspeakers and Rooms) in chapter (13). Toole shows actual measurements and performance gains in his real world room which was far more complicated than a simple rectangular room. He showed how using 4 subs with SFM (Sound Field Management) could be made to solve a very complicated room geometry/enviroment. Basically as you have done also they adjusted placement, level, phase, and used a PEQ filter on each sub to acheive a much improved listening area.

As a side note: I really can't encourage it enough that if anyone is really interested in getting a deeper understanding of this hobby then you owe it to yourself to read this book..!

I would also like to say that if all one is concerned about is one listener location then a single sub(s) location with proper EQing can give very good results.

mike tn

Edit: Michael and Rudy I want to add that no doubt trying different locations can get very complicated and if someone finds what makes them happy then it makes alot of sense to just stop and enjoy the music..!